Electron discharge device



prilzs, 1950 H, F, ENGELMANN 2,504,970

i ELECTRON DISCHARGE DEVICEl Filed 001;. 5, 1945 ATTORNEY Patented Apr.. 25, 1950 OFFICE ELCIIRQN:` D'ISCHARGFL DEVICllr Herbert Engelmann, New York; Nl Y., assignor vtoi,'Federal.1.'Iele1ihone and Radiof Corporation,; New-,.York. N.; a: corporation of .DelawareI MyI f iriiventlorrv relates 4to electrons,- discharge tained.' A= slightfvariation offfiield"strength,l forV examplefnear anode currentout-off; marconi;-` pletely change the mode 'and 'the firequencyfof oscillation. Instability becomes particularly manifest .whenfone tube issubstltutedforr'another in its "mounting. Thefm'agnetlzing meansv of the usual magnetron. is'farcoiltelescoped over'tlie envelope andis Vemitirely'erter-nal: to the evacuated `space lof the ztube; so'fthat lthe distancesbetween the electrodes :andv the. coil: cannot lbe accurately established. in.. manufacture; l

Axstill further disadvantage fof .thefconvlens tionalmagnetron oscillator resides .inthevusually poor electrical connection: betweenfsegments ofl the anode where eachranodef is"sp1itr1 on' divided ,36

into two or more electron collecting sections?` For yeflicientoperation. at ultra-'high frequencies, it is important that therel be--no impedance norpliaseVv differenti-ation between the different. sections@ of an.- anode; v

An -obiect ofl my; inventionwis ani improved l magnetron-.-

Another: cbiect off` my' inventionv arrlrnproved unitary f magnetron and` magfnetroir.:` mounting.

Another object-of@myiinventionsra'magnetron tolerances;

A` stmfurtheromector mvLinventfon-Ji .a mag; rletronl with simple yeti 4impedance#free connec-v tions between the segments offtlie anode.-A

- i invention is defli'lelzl-"finF` theappendedclaiins' and ones ernbodimentl isdescribedfinffthe fol-lover"-` into the lleaved` se-L 2 ing specication and show-n in the accompanying drawing in which Fig. l is a lengthwise sectioned view oi? my novel magnetron tube and itsV mountingand Fig; 2` is a horizontal section taken on line 2`-2 The device `ofmy novel magnetron oscillator comprises a tubularcathode sleeve l coaxial with the circularly arranged and inter= -ents l andre of anodes 2 and 3.V The cnveiope for the electrodes comprisesr glass annulii a hermeticallfy sealed to the metal parts of the tube. An exhaust tubulation Smay ce joined to one of the glassportions for exhaustingenti sealing the envelope.

catlflcde,v according to one importantl fea.-

'ture of miv novel magnetron comprises a rigid metal sleeve or Vtube 'exteriorly sensitized with electron emittingl material and adaptedfor ine direct heating with an interiory heatngccv IU. Byi connecting'oueendof the heating coil to the sleeve, two lead-in conductors' l I vmay suffice for the cathode and itsheater. The lead-ins are' sealed through a glassbutton-type header I2; If additional support. for the cathodeassembly is desireda 'stud may be attachedtothe sleeve and embedded-'in the header;` Since the diameter of tliecathode' is relatively large; the ends of the sleeve are V'preferably `closed to conserve heat and preventrandorrr electron emission from the coil.

The magnetron `ancdes each comprise an al1-'- nulus having spaced opstanding integral projectionsor'segments along'the inner periphery of theannulus opposite the cathode. The. inner peripheries `oi`^`the annuli are of the. same diameter so that thefanode vsegments may interleave andi lie in' acomm'on circular surface. The' anode segments? are: an lintegral partI of and aresup ported' noon annular lead-infcondu'ctors lil` and te sealedradially through;4 the envelope: The outerr periphery' of' the' anode: annuli press against the'concentric/conductors l5`and` I'E of a cavity resonator or^transmission line. TheA usual straps complicated' "connectionsy of' 'the' conventional ysplit anode magnetron are eliminated in my tube'.

Accurate-placement and control of thefmag# neti'c- 'eld within Vthe annularl discharge Space is effected by' magnetic plugs 'or' stoppers1l1`and l-E' hermetically sealed tlirouglith'e ends of the envelope; The'stoppersniay be ofiron, nickel, 'cobalt'ystoel vor any of thenaramagneticalloysz `stopjlcers `are round; coaxial' withv the cathode, terminate adjacent the ends of the cathode,` and have1 af diameter slightly' less than the'inner'd'- 1w ameteroi the anode. When? av magneticl poten-"- according to my invention may be replaced inv service without changes in mode .of oscillation and without laborious readjustment of power supplies lor the cathodes, anode and magnet.

The outer ends of the magnetic Stoppers are preferably machined and polished to make good 4 a point of voltage maximum to couple the oscillator with its load circuit. The tubes I5 and IB could of course be extended into the endless conductors of a coaxial cable.

In operation, the anode voltage and the magnetic field strength are preferably adjusted so that space current cut-oir just occurs, whereupon the electrons bunch and travel in circular paths about the cathode in planes substantially perpendicular to the axial line of the tube. Such an orbit carries the electrons successively past the segments of anodes Zand 3, and as the electron transit time between segments approaches the resonant fre- "j quency of the .connected tank circuit I5-I6, the

vvoltage induced in one set of segments, 4, becomes 180 degrees ldisplaced from the voltage induced contact with the ends of the yoke. One leg of the l yoke may be hinged as at 2l to permit easy replacement of the tube.

The stopper in the lower or base end of the envelope is-ccnveniently annular in shape to accommodate the insulating header and the cathode leads, and to shape the magnetic eld to the annular anode-cathode space. If desired the inner face of the upper stopper may be recessed to provide a rim opposite and complementary to the end'of the lower stopper. Accordingly, the pole pieces of my improved magnetron may be brought elose'to the discharge space to accurately localize the eld in the space. Less magnetizing power is required for a given eld strength in the gap and less disturbance of the field is possible from extraneous sources.

My improved magnetron is simple and inexpensive to make, being adapted to the manufacturing technique of the conventional radio receiving tube. The header is rst press molded in the lower stopper with the cathode leads. The cathode sleeve is then assembled with its heater coil and their two connections spot welded to the inner ends of the leads. This subassembly may then be telescoped with the glass rings 6, 1 and 8 and metal annuli I3 and I4, conventional jigs being used for accurately spacing and holding the parts in alignment while the rims of the glass rings are melted and sealed to the adjacent metal surfaces. In case the glass is hard and the stopper-s are of iron, it may be expeditious to make the glasstoiron seals with pleated copper rings 22, which are feathered along one edge for the glass seal, the other edge being easily brazed vacuum tight to the iron.

^ An important feature of my magnetron osciliator is its cavity resonator exterior of tube envelope,and the easy adjustability of the chamber length. Concentric tubes or lines I5 and I6 make contact, throughout the peripheries of their upper ends, with the rims, respectively, of the anode annuli I3 and I4. The very source of high frequency electromotive force is accordingly effectively brought to the end of the resonator, with no resistive losses and with no impedance or phase shift. Yet, notwithstanding the structural compactness of oscillator, the discharge device may be removed and replaced as a conventional radio f receiving tube in its socket. One advantage oi' the resonant chamber outside the tube envelope is its easy adjustability. Piston 23, with spring lingers, may be slid along the annular cavity with piston rods 24. Since one current maxima is at lthe short circuited end of the line, a current pick up coil 25 may be carried on the piston and exteriorly connected by means of twisted conductors in the piston rod. Alternatively, a capacity probe, notshown, may be inserted into the cavity at, say,

inthe other set, 5. ,Whether this or other modes ofl operation be employed, each segment of either ariode' delivers in-phase power to the adjacent end of the concentric line, I5 or I6. The number of segments per anode or the size of the anodes are not limited by any particular mode of oscillation, and, in fact, as the anode is made larger, with more segments, the anode supply voltage becomes proportionately less. Further, because of the low impedance of the connections between the segments-and the resonant chamber, the decrements of the circuits are low and the electric coupling is close between the anodes and frequency determining means. Accordingly, the oscillator may be tuned by the piston 23 over a wide range of frequencies without loss of control of the electron oscillations.

My invention extends the power range of the magnetron by permitting the use of a large indirectly heated cathode without disproportionately increasing the anode voltage. My magnetron can be manufactured inexpensively, yet with close tolerances, even in the magnetic circuit. The built-in magnetic gap insures stable operation, and uniform characteristics as between tubes. Stability, further, flows from my novel way of electrically joining the anode segments to eliminate unwanted phase diiierences.

I claim:

1. An electron discharge device comprising an indirectly heatedpcathode sleeve, a flat metal annulus disposed in a planev normal to the axis of said sleeve, a second annulus with a larger outer peripheral diameter parallel to and spaced from the iirst mentioned annulus, each annulus having integral upstanding projections along its inner periphery and mounted in a cylindrical'surface concentric with the surface of said` sleeve, the projections of one annulus alternating, circumferentially, with theY projections of the other` annulus, cylindrical Stoppers of 'magnetic material coaxial with said sleeve and closely disposed to opposite sides of the annulur space between said sleeve and said projections, and insulating envelope wall portions hermetically sealed between -the faces ofv said annuli-andthe sides of said Stoppers f 2. The electron discharge device defined -in claim -1,- in which said cylindrical Stoppers are of a metal principally of iron and which further includes rings of thin sheet metal with circumferential pleated folds, each of said rings being vher-- 75.metically-sealedalong one edge to` one of `said Stoppers and along its other edge in one of said insulating envelope wall portions.

HERBERT F. ENGELMANN.

REFERENCES CITED The following references are of record in the le of this lpaltent:

UNITED STATES PATENTS Number Name Date Jurriaanse Nov. 1, 1938 Berline July 29, 1941 Potts July 4. 1944 Goodchild Feb. 19, 1948 Number 10 Number Name Date Spencer Sept. 24, 1946 Morton Oct. 15, 1946 McArthur et al. June 3, 1947 Hansell July 29, 1947 Nelson Oct. 14, 1947 Burns Dec. 9, 1947 FOREIGN PATENTS Country Date Great Britain July 7, 1936 OTHER REFERENCES Electronics, February 1945, pp. 98-102. 

